1. Field of the Invention
The present invention relates to an apparatus which evaluates a motion state of a legged mobile robot.
2. Description of the Related Art
As a technique for performing a motion control of a legged mobile robot (hereinafter referred to simply as a robot in some cases), there has conventionally been known a technique disclosed in, for example, Japanese Patent Official Gazette No. 4246638 proposed by the applicant of the present application. In this technique, the state amounts related to the posture of a robot (for example, the posture of the upper body of the robot) are sequentially observed during operation of the robot in order to prevent the posture of the robot from being unstable due to an error or the like between the configuration of a floor assumed in a desired motion of the robot and an actual configuration of the floor. Further, as a feedback manipulated variable for bringing the difference between the observed value of the state amount and a desired value of the state amount defined by the desired motion of the robot close to zero, an additional floor reaction force applied to the robot (a floor reaction force added to a basic floor reaction force for achieving a desired motion) is determined. Then, the actual motion of the robot and the floor reaction force actually applied to the robot are controlled to follow the desired motion of the robot and the desired floor reaction force with the additional floor reaction force added thereto, respectively, thereby causing the robot to implement the motion smoothly.
To cause the robot to perform a variety of jobs, there are cases where it is required to cause the robot to perform a required motion while maintaining a plurality of portions of the robot in contact with a plurality of surfaces to be contacted existing outside the robot (e.g., maintaining the distal end of a leg and the distal end of an arm of the robot in contact with a floor surface and a wall surface, respectively), rather than simply causing the robot to travel on a floor.
In this case, unlike the case where the robot simply travels on a floor, external forces act on a plurality of portions of the robot from the plurality of surfaces to be contacted in an outside world of the robot.
Therefore, in such a case, in order to control the robot to operate properly, it is necessary to properly set targets, including a desired external force and the desired position of the action point of the external force, related to external forces to be applied from the plurality of surfaces to be contacted and to perform a motion control of the robot so that external forces applied from the plurality of surfaces to be contacted to the robot follow desired external forces while causing the actual motion of the robot to follow the desired motion. In such a case, it is desirable to set the target related to the external forces with adjustment to prevent the actual value (observed value) of a required motion state amount of the robot from deviating from the desired value.
However, when the external forces act on the robot from the plurality of surfaces to be contacted, as described above, unlike the case where only a floor reaction force acts on the robot, it is important to adopt what external forces to which the external forces acting on the robot from the plurality of surfaces to be contacted are adjusted in order to reduce a difference between the actual value (observed value) of the required motion state amount of the robot and the desired value in the case where the actual value deviates from the desired value.
Further, in this case, for external forces actually applied to the robot, additional external forces for reducing a deviation in the motion state amount are added to the external forces to be applied to the robot in order to achieve an intended desired motion (a motion based on the assumption that the above motion state amount coincides with the desired value), and therefore it is frequently required to evaluate the motion state of the robot such as to evaluate whether the additional external forces are able to be added to the robot without interfering with a smooth motion of the robot.
Hitherto, however, techniques have not been fully studied on manipulating the external forces, which are to be applied to the robot, according to a predetermined motion state amount of the robot while implementing a motion of the robot in the situation where external forces act on the robot from the plurality of surfaces to be contacted, as described above. Consequently, in an actual situation, techniques have not been fully studied, either, on properly evaluating whether the external forces are able to be manipulated without interfering with a smooth motion of the robot when the above external force manipulation is performed.